When we are measuring the passive pressure we are measuring the resistance of the soil against wall movement.

Hence for all practical purposes we get fully mobilised active earth pressure but partially mobilised passive earth pressure as such a large movement does not occur usually. Hence it is more acceptable to design with active earth pressure.

Thus when is reached active pressure is fully mobilised but passive pressure is partially mobilised. Therefore we should design with ( – a small % of ), as, we are making an unsafe design when we are designing with
( – fully mobilised ) and an uneconomic one when we are designing with only .

To get fully mobilised active and passive earth pressures the following wall movement are required approximately.

= (0.1 - 0.4)% of the height of the wall.

= (5-10)% of the height of the wall.

For dense sand mobilised at 0.1% strain and at 5% strain.

For loose sand mobilised at 0.4% strain and at 10% strain.